01 May, 2020
Our paper on adjoint tomography for the Kanto region won a 2019 Seismological Society of Japan Paper Award:
Takayuki Miyoshi, Masayuki Obayashi, Daniel Peter, Yoko Tono and Seiji Tsuboi
Adjoint tomography of the crust and upper mantle structure beneath the Kanto region using broadband seismograms
Progress in Earth and Planetary Science (2017) 4:29 10.1186 / s40645-017-0143-8
Award text (auto-translated by google):
Estimating the Earth's internal structure by the waveform inversion method requires high-speed, large-capacity numerical calculations, so its application to actual structures has been limited. In this paper, the waveform inversion method is applied for the first time to the complex crust and upper mantle in the Kanto region where two plates are subducted, and the obtained three-dimensional velocity structure is geologically shown while quantitatively showing the reproducibility of the observed waveform. This is a highly pioneering paper that has been successfully interpreted in a comprehensive manner.
In this paper, running tomography is applied to about 4400 waveforms acquired at 16 F-net stations around the Kanto region for 140 seismic events by applying the acjoin tomography method, which is a type of waveform inversion method. The velocity structures of P wave and S wave were estimated using the existing three-dimensional structure obtained in the above as an initial model. For the analysis, a three-component displacement waveform of 5 to 30 seconds was used, and forward calculation and finite calculation were performed by the spectral element method using a mesh structure expressing the Kanto region with 16 million nodes. Using the "K computer" of RIKEN, 16 iterations were performed by a total of 6720 simulations and a large-scale calculation of about 62,000 node hours, and the final velocity structure model was obtained. The velocity structure model in this paper was obtained from the waveform data of only 16 observation points, but the waveform reproducibility was improved by 24% compared to the initial model using the running data of more observation points. This shows the usefulness of this new method. Furthermore, the waveforms for 18 seismic events not used in the analysis were predicted, showing that the waveform reproducibility was improved by 47% compared to the initial model. The three-dimensional velocity inhomogeneous structure obtained in this paper shows a spatial pattern consistent with the initial model, but detects an S-wave velocity anomaly region that is significantly slower than the initial model. It shows the possibility of detecting the existence of serpentinite and volcanic activity with higher resolution.
With the recent development of traveling tomography, seismology has played an extremely important role in deepening the understanding of the interior of the solid earth. Against the background of recent advances in supercomputers, this paper, which pioneered a new method called the waveform inversion method, has the potential to bring new understanding of the Earth's interior beyond the limits of existing methods. , It has great significance for future internal structure research.
For the above reasons, this paper will be awarded the 2019 Seismological Society of Japan Paper Award.
reading in Japanese: